The correct answer is option Observations can be made from outside the "system".
The study of the plate tectonics allows the observation of the movement of the plate tectonics. These observation can be study to determine the pattern of the movement from outside the plate tectonics system and the event occurring due to plate tectonics can be predicted.
 
        
                    
             
        
        
        
You didn't provide us with any possible ways? Primary reinforcers are, however, types of reinforcers where they immediately elicit a reward or reward-like behavior once they are applied in a situation. An example would be apple juice. 
Secondary reinforcers on the other hand need to be associated with something for them to become reinforcers or they provide rewards in a non-direct way. An example would be money.
This is the main relationship between them.
        
                    
             
        
        
        
The nucleus is important to a living cell because <span> it serves the function of information storage, retrieval and duplication of genetic information. It is a double membrane‐bound organelle that harbours the genetic material in the form of chromatin.</span>
        
             
        
        
        
2 is the answer I THINK look at other ones first 
        
             
        
        
        
Answer:
There are many explanations.
Explanation:
1) It is "the chemical sodium thiosulphate (formerly called hyposulphite) used as a photographic fixer."
2) another word for hypodermic
3) an attack of hypoglycemia
4) under; below
Hope this helps you! ;)